Vincent Nyasembe: When chemical ecology meets enduring dream for public health improvement
At the age of seven, Vincent Nyasembe contracted malaria and found himself hospitalised for three months, an episode that impacted significantly on his life and career.
“I remember that period vividly and with a sense of trauma. My symptoms were evident and consistent with malaria, but somehow it took that long for me to reach full recovery. Even at such a young age, I could tell that there was a serious problem somewhere. Lying in that hospital bed, I resolved that I would become a doctor, to contribute to a situation where people would not have to go through my experience,” he recalls.
Vincent’s decision was especially pertinent considering that he was born and raised in western Kenya, a malaria endemic region. And although his goal was set at such a tender age, the determination to join the medical profession stayed with him throughout his primary and secondary schooling. However, his O levels, completed in 2002, did not qualify him for a degree in medicine. Not to be deterred, Vincent enrolled for a BSc in biomedical sciences at Egerton University, Kenya, reasoning that the course would still present a chance for him to contribute solutions to control malaria.
After graduation in 2008, opportunities in the world of research were not forthcoming straightaway, and Vincent, whose family had by then moved to a low-income neighbourhood in Nairobi, held positions as a laboratory technician and a part time high school teacher. His big break into research came through a six-month Consortium for National Health Research (CNHR) internship tenable at icipe. Under the mentorship of Prof. Baldwyn Torto, Head of the icipe Behavioural and Chemical Ecology Unit (BCEU), he conducted research under two projects: one on human odour attractants, and the other on insect growth regulators. Both projects enabled him to acquire skills in chemical ecology and insect physiology, which provided him with strong foundation for postgraduate research.
Upon completion of the internship, with Prof. Torto’s assistance, Vincent enrolled for an MSc in medical entomology at the University of Nairobi. His thesis project focused on plant feeding behaviour of mosquitoes. From the study, he observed an interesting phenomenon in malaria mosquito-parasite interactions: that Plasmodium, the malaria causing parasite, alters the feeding behaviour of mosquitoes, and enhances the attraction of the insects to plants. These findings, published in the prestigious Current Biology journal, earned Vincent the icipe Governing Council best published paper students’ award in 2014. In addition, the study identified plant chemical signals that attract malaria carrying mosquitoes, and led to the formulation of blends that could be used to sample and observe the vectors in the field.
During a brief tenure as a research assistant, Vincent and colleagues in BCEU established that Parthenium hysterophorus, an invasive weed spreading rapidly across East Africa, which negatively impacts on agriculture could increase malaria incidents. This is because the weed can sustain the malaria-transmitting mosquito, Anopheles gambiae, by extending its life even in the absence of a blood meal.
Vincent was then accepted as an icipe PhD researcher, through the Centre’s African Regional Postgraduate Programme in Insect Science (ARPPIS), and support from the Swedish International Development Cooperation Agency (Sida), registered at the University of Pretoria, South Africa. Under the supervision of Prof. Torto and Dr David Tchouassi at icipe, alongside Prof. Christian Pirk and Prof. Catherine Sole from the University of Pretoria, he advanced his research by studying the nectar feeding behaviour of Afrotopical mosquito species. The goal of the studies was to develop and evaluate nectar-based lures for the management of key mosquito species vectoring Rift Valley fever, dengue and malaria.
“Previously, there had been no clear way of pinpointing how mosquitoes select host plants. Using DNA barcoding, we could to detect plant tissue in mosquitoes, identify plants that the vectors feed on in their natural habitats, and establish the unique fragrances in each of these plants that attract mosquitoes. Although the same strategy had been used for other insects, this was the first time it was being applied to mosquitoes. In addition, contrary to the hypothesis that mosquitoes rely only on blood for nutrients such as amino acids, we found out that these insects can also obtain specific amino acids from plants, albeit in minute amounts,” explains Vincent.
The study identified the natural host plants of the mosquito species that transmit malaria, dengue and Rift Valley fever. It also confirmed linalool oxide, a pleasantly scented compound found in many flowers and spices, to be attractive to the vectors. Based on the findings, Vincent and colleagues in BCEU formulated lures that are attractive to Aedes aegypti mosquitoes, which transmit Rift Valley fever among other diseases. The lures are now undergoing further studies.
Having completed his PhD studies in early 2017, Vincent is currently undertaking a postdoctoral fellowship at the University of Florida, USA, to advance knowledge on previous findings by investigating the mechanism through which Plasmodium infection increases the attractiveness of infected mosquitoes to host plants.
Asked if he regrets not having realised his childhood vision of becoming a doctor, Vincent observes: “Not at all. Indeed, I am gratified to have still been able to pursue a career in public health, focusing on vector control, one of the main tools for eliminating diseases such as malaria.”
He also commends the icipe postgraduate programme for its key role in developing his career as a researcher, noting: “The Centre offers international training standards, a conducive atmosphere, and a chance for young researchers to forge global networks. For instance, in 2016, I received a travel award to participate in the highly prestigious International Society of Chemical Ecology and International Congregation of Entomologists, where I made presentations on the key findings of my PhD study.”
Vincent intends to use his current fellowship to nurture his research career and international connections, before returning to Kenya to continue his research. In addition, mindful of the opportunities and mentorship that have shaped his own career, he would like to help mentor a new generation of scientists in Africa.